Coloring materials are used for a variety of applications, particularly in the food industry. Yellow-red colors are of great importance to the food industry and are used, e.g. to impart more “natural” colors to carbonated drinks, soups and a wide variety of food products. In recent years the food industry has experienced a shortage of yellow-red coloring materials, due to the fact that a number of synthetic food colors have been suspected of carcinogenic activity, and the use of some of these materials has been prohibited by health agencies.
The art has failed so far in providing versatile coloring materials in the yellow-red color range from natural sources, which are not suspected of being harmful to health. In some instances, β-carotene, extracted from natural sources e.g. algae, is used as a natural coloring material for the orange-yellow color range. However, known natural materials often suffer from various severe drawbacks. In general, their use is very expensive since their coloring potency is inferior to that of synthetic colorants. Furthermore, many natural colors are pH-dependant and thus change their color after incorporation within food products as a result of pH changes, or due to oxidation in air, and are often readily destroyed by moderate heat.
One candidate for use as a natural coloring material is lycopene, which like β-carotene, belongs to the family of the carotenoids. These pigments are found in higher plants, algae, bacteria and fungi, and are synthesized intracellularly within particulate organelles called chromoplasts. Lycopene has the formula:
and can be found in many plant sources, including tomatoes and watermelon. Lycopene is the compound which imparts the bright red color to these fruits, but conventional methods of extraction destroy the crystalline structure of this pigment, thus altering its red color to orange-yellow, similar to the color obtainable with β-carotene.
In addition to its use as a coloring agent, lycopene is known to be an effective natural antioxidant and quencher of free radicals, especially those derived from oxygen. These properties are due to the unique chemical structure of lycopene, which is a long hydrocarbon chain consisting of eight isoprene units, containing 11 conjugated double bonds and 2 non-conjugated double bonds. In humans, reactive oxygen species, including free radicals, are formed as a natural part of the oxidation process, but in a healthy organism, these molecules are neutralized by a complex system of enzymes and antioxidants before they can incur damage to cells and tissues. However, excess of reactive oxygen species, expressed as oxidative stress, appears to play an important role in the initiation and promotion of cancers, atherosclerosis, arthritis and other degenerative diseases. At the same time, overwhelming evidence exists in the scientific literature that diets rich in vegetables and fruits are associated with lower risks of the development of these degenerative diseases. Moreover, the role of lycopene in conferring protection against such conditions, due to its antioxidant properties, is strongly suggested by numerous research efforts. Reviews which address this topic and contain extensive bibliography are: “Lycopene: Chemistry, Biology and Implications for Human Health and Disease”, in Nutrition Reviews, Vol 56, No. 2, February 1998, pp. 35-51, by Steven K. Clinton; “The Potential Role Lycopene for Human Health”, in Journal of the American College of Nutrition, Vol. 16, No. 2, 1997, pp. 109-126, by Helga Gerster, and “Tomatoes, Tomato-Based Products, Lycopene and Cancer: Review of the Epidemiologic Literature”, in Journal of the National Cancer Institute, Vol. 91, No. 4, Feb. 17, 1999, by Edward Giovannucci.
Lycopene is a normal constituent of human plasma, and is found therein in concentrations greater that that of any other dietary carotenoid. In addition, its ability to neutralize reactive oxygen species is more effective than that of β-carotene or any other tested carotenoid. Since lycopene is not synthesized by the human body, it must be obtained from dietary sources, such as tomato. It thus becomes evident that a concentrated lycopene preparation could be useful not only as a natural coloring agent, but also as a health-promoting natural “nutraceutical”. Nutraceuticals are an emerging class of dietary supplements, which are foods or parts of foods having specific health benefits, including the prevention or treatment of disease.
Processes are known in the art for extracting and concentrating carotenoids from natural sources and processed food products. Chromoplasts, the organelles containing carotenoids, may be isolated from tomato fruits on the basis of their characteristic density via a biochemical procedure involving Percoll density gradient centrifugation. Although this method has enabled study of the biochemical changes occurring during the ripening process, such a method is not suited to the food processing industry which demands large scale application and the absence of biochemical reagents which could compromise human health, and/or impart an undesirable taste to the final product. Similarly, carotenoid compounds have been isolated from various processed tomato-based food products via biochemical methods employing volatile solvents. Such analytical scale techniques have proven useful for quantifying carotenoid concentrations for the purpose of enlarging nutrient survey and food composition databases, but are not suitable for industrial scale production of an additive-free food coloring material.
U.S. Pat. No. 4,726,955 relates to a process for the preparation of pulverant carotenoid preparations for food coloring agents. The process utilizes organic solvents for dissolving the carotenoids, followed by their colloidal dispersion with milk products.
U.S. Pat. No. 5,245,095 relates to a solvent-free method of extracting carotenoids from natural sources, particularly carrots. The carotenoids are precipitated from a liquid fraction of the juiced source material using a calcium salt precipitating agent. This method is not suitable for the extraction of lycopene from tomatoes, since in that fruit, following breakage and separation into liquid (serum) and solid (pulp) fractions, practically all the lycopene is found in the pulp and only a minute quantity is found in the serum. Furthermore, growing consumer demand for safe and additive-free food coloring materials make both the above methods deficient, and unlikely to withstand scrutiny from public health interest groups.
Many processes are also known in the art for producing tomato pastes and concentrates, products which do indeed contain high concentrations of lycopene. However, these products also contain high concentrations of those tomato components which contribute aroma, viscosity and flavor to the final product. These latter properties are contributed by the soluble solids present in tomato. In the tomato, soluble solids constitute about 5% by weight of the whole fruit. (All percentages, as well as parts per million (ppm) in this specification and claims are by weight, unless otherwise specified). The insoluble solids, which include the lycopene-containing chromoplasts, constitute about 1% of the weight of the fruit, while the remaining 94% is contributed by water. In the production of tomato paste, only water is removed, thus increasing the concentrations of both the soluble and insoluble solids by the same ratio.
In the field of food technology, the soluble solids content of foods is frequently reported in degrees Brix, (° Bx) which is a measurement of the light refraction of the dissolved solids, expressed as sucrose. While a native whole tomato contains approximately 5° Bx of soluble solids, commercially available tomato pastes contain about 30° Bx. Similarly, while a native whole tomato typically contains approximately 70 ppm lycopene, commercially available tomato pastes contain approximately 350 to 400 ppm lycopene. Hence, while tomato paste is enriched about 6-fold in lycopene concentration, taking into consideration losses incurred upon processing, tomato paste is also enriched about 6-fold in the concentration of the components which contribute tomato flavor.
Thus, while prior art processes such as those disclosed in U.S. Pat. No. 3,864,504, U.S. Pat. No. 4,670,281 and U.S. Pat. No. 5,229,160 may be efficient for producing good quality tomato concentrates with high color value, none of the products of these inventions could be utilized solely as a food coloring agent. A food coloring agent should be versatile, and therefore devoid of the aroma and flavor of the source from which it was derived. Likewise, U.S. Pat. No. 4,181,743 relates to a method of processing plant products, including tomatoes, to produce flavoring extracts from their juices. Obviously, such a product could not be used as a coloring material, since it will impart both color and flavor to the food product to which it is added.
It is therefore clear that it would be highly desirable to provide a coloring material from natural sources, particularly tomatoes, which is capable of imparting a red color to food and other products, yet is largely devoid of other properties of the source from which it was derived, such as texture, aroma and flavor, and does not present the problems inherent to prior art colorants. It is an object of the present invention to provide such novel coloring materials, which can be safely employed as colorants in a variety of food products.
It is an object of the present invention to provide such novel coloring materials, such that the concentration of coloring material of the invention is at least 10-fold that of the native fruit source material from which it was derived, while at the same time, the concentration of soluble solids in the coloring material is no greater than the concentration of soluble solids in the native fruit source material from which it was derived, and optionally less than said concentration.
It is an object of the present invention to provide such novel coloring materials without the use of exogenous reagents, so that such coloring materials can be safely employed as colorants in food products.
It is another object of the invention to provide natural coloring materials which overcome the drawbacks of prior art materials, which present improved stability to pH changes and heat processing, and which can be used in a variety of food products.
It is still another object of the invention to provide a process for preparing such novel coloring materials.
It is a further object of the invention to provide food products to which a desired shade of red has been imparted by the coloring materials of the invention, while not imparting flavor of the source from which the coloring materials were derived.
A major advantage of the present invention is that it provides a concentrated form of a natural phytochemical which has health promoting properties. Hence, reference herein to the natural coloring materials of the present invention also refers to a food-derived preparation which is beneficial to human health and can be utilized as an agent for promoting and maintaining human health i.e. a nutraceutical.
Other objects and advantages of the invention will become apparent as the description proceeds.